This invention relates to optical systems in general, and more particularly to wavelength monitoring systems.
In many situations, it is necessary or desirable to monitor the wavelength of a beam of light.
By way of example, in wavelength division multiplexed (xe2x80x9cWDMxe2x80x9d) optical network systems, multiple optical signals can be simultaneously transmitted (or xe2x80x9cmultiplexedxe2x80x9d) on a single optical fiber. Such multiplexing is performed by simultaneously transmitting the different optical signals down the optical fiber at different wavelengths (or xe2x80x9cchannelsxe2x80x9d). The different optical signals are subsequently de-multiplexed by selectively filtering a desired signal from the group of signals, based on the particular wavelength (or channel) of the target signal. Therefore, in such optical network systems, it is desirable to facilitate the monitoring of different signals at different wavelengths (or channels) on an optical fiber.
Accordingly, one object of the present invention is to provide novel apparatus for monitoring the wavelength of a beam of light.
Another object of the present invention is to provide novel apparatus for monitoring the wavelengths of different optical channels transmitted through a WDM fiberoptic system.
And another object of the present invention is to provide novel apparatus for continuously monitoring the wavelengths of different optical channels transmitted through a WDM fiberoptic system.
Still another object of the present invention is to provide a novel method for monitoring the wavelength of a beam of light.
Yet another object of the present invention is to provide a novel method for monitoring the wavelengths of different optical channels transmitted through a WDM fiberoptic system.
And another object of the present invention is to provide a novel method for continuously monitoring the wavelengths of different optical channels transmitted through a WDM fiberoptic system.
These and other objects are addressed by the present invention, which comprises the provision and use of a novel wavelength monitoring system for monitoring the wavelength of at least one optical channel transmitted through an optical system.
In one form of the invention, the novel wavelength monitoring system comprises an optical diffraction grating, a rotating polygon having a reflective mirror on each facet thereof, and an avalanche detector positioned behind a slit; wherein the optical diffraction grating receives the light which is to be monitored from the optical system, disperses that light, and projects the dispersed light onto the rotating polygon; and wherein the mirrors of the rotating polygon reflect the dispersed light coming off the optical diffraction grating so that the dispersed light passes through the slit and falls onto the avalanche detector; such that the output of the avalanche detector peaks every time a streak of light, corresponding to a different wavelength at a designated channel, passes by the detector.
In another form of the invention, the novel wavelength monitoring system comprises a hollow, transparent cylinder having a thin film filter deposited on a surface thereof, a motor, and a detector; wherein the thin film filter is a Fabry-Perot structure having a gap which varies as a function of its position on the rim of the cylinder, such that the varying gap allows for a varying transmission wavelength which varies as a function of angular position; and wherein the light passing through the thin film filter falls on the detector.